SoftBank Group Corp. has quietly amassed a $4 billion stake in Nvidia Corp. making it the fourth-largest shareholder in the graphics chipmaker, according to people familiar with the situation. The Japanese company, which just closed its Vision Fund, disclosed it owned an unspecified amount of Nvidia stock when it announced $93 billion of commitments to the technology investment fund on Saturday. A holding of 4.9 percent, just under the amount that would require a regulatory disclosure in the U.S., would be worth about $4 billion. [ Bloomberg ]